Chromium complex coupling agent

At one time these were the only commercially important non-silane coupling agents. Supplied by du Pont under the Volan tradename, they are coordination complexes of carboxylic acids with chromium(III) chlorides. Hydrolysis of the... 

Other coupling agents, based on chromium complexes (Figure 4) have been used in the past to promote adhesion between glass fibres and resins, but at present organosilanes are the preferred choice. 

Efficient coupling agents are silanes [1,55,62,69-71] and organotitanates [72-74], which are easily dispersed and present a high chemical resistance. Chromium coordination complexes and substances containing phosphorus are also used. 

Chromium coordination complexes with compounds containing — NH2, — NH—, epoxide, amide, and isocyanate groups [52-54] are also used. Cation active substances such as cationic styrene aminosilanes are recommended by Dow Coming (U.S.) as coupling agents. For example. 

The first successful glass fiber treatment found was a chromium complex of methyl-methacrylate. The initial versions of feis product were the first coupling agents and reduced the strength losses under humid conditions to about 40%. This chromium-based chemistry was improved and later commercialized by DuPont and is still in use wife glass fiber to some extent today. 

As mentioned earlier, these were the original coupling agents for use in polymer composites. Salts of trivalent chromium can be reacted with certain organic acids to produce cyclic complexes, such as shown in Fig. 22.12. If the acid carries a polymer reactive functionality, this can be incorporated into the complex. The reaction between chromium chloride and methacrylic acid is particularly suitable, resulting in a complex with reactive unsaturation. This complex can react with inclusion surfaces through the chromium functionality and with suitable polymers through the unsaturation. 

Many metals are used as chromophores. These can include, but are not limited to, cobalt, nickel, iron, chromium, tungsten, ruthenium, gold, copper, vanadium, titanium, manganese, zinc, aluminum, zirconium, palladium, and tin. Organometallic complexes with these metals are often used as coloring agents for a variety of materials. Coupled with the appropriate ligands, they can be made soluble in a slew of solvents and so can be distributed to wherever they are needed. 

Fluorinated dithiocarbamates have been used as part of a supercritical fluid extraction (761), while pyrrolidene (762, 763), and benzyl (741, 764) dithiocarbamates and poly(dithiocarbamate) chelating resin (765) have also been utilized, as has detection by XRF (764) and inductively coupled plasma atomic emission spectroscopy (765). Related to this, the determination of chromium levels in urine has been achieved using lithium bis(trifluoroethyl)dithiocarba-mate as the complexing agent with detection via an isotopic dilution GC and mass spectral method (766). 

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